DropDown is an ASP.NET AJAX extender that can be attached to almost any ASP.NET control to provide
a SharePoint-style drop-down menu. The displayed menu is merely another panel or control. In the
above sample the drop-down is a Panel which contains LinkButtons. The drop-down is activated by left-
or right-clicking the attached control. If the behavior is attached to a Hyperlink or LinkButton,
clicking on the link itself will operate normally.

DropDown Properties

The control above is initialized with this code. The italic properties
are optional:

OnShow - The OnShow animation will be played each time the dropdown
is displayed. The dropdown will be positioned correctly but hidden. The animation can use
<HideAction Visible="true" />
to display the dropdown along with any other visual effects.

OnHide - The OnHide animation will be played each time the dropdown
is hidden.